Edit: By the way, have a look at this: http://arxiv.org/find/all/1/all:+AND+kane+AND+kumar+acharya/0/1/0/all/0/1 a list of papers relevant to this topic.
This post is intended to dismiss some of the claims that “String Theory isn’t testable“;. So, let’s first list out some of the claims we hear about the experimental testability of String Theory, in random discussions, on comments by trolls on tRF , and by the well-known crackpots, (dubbed “Smoit”, but I suggest “Woilin”):
- String Theory disagrees with well-known Physics!
- Ya, whatever, fine, but it agrees with everything, so that basically means that String Theory isn’t testable! It’s like, pseudo-science!
- Ok, ok, but it isn’t testable at today’s energy scales, alright? Ha!
- Well, fine, whatever, but it has been experimentally disproven!
- Ok, fine, WHATEVER, but it hasn’t been experimentally proven, at least, ok? Ha! How will you counter that?!
Ok, so let’s counter each of them.
String Theory does agree with well-known Physics.
It is a trivial excercise to show that String Theory agrees with General Relativity.
One starts with the beta functionals, which describe the breaking of conformal symmetry due to the presence of the Dilaton. To keep Conformal Symmetry, these functionals must be set to be 0.
The coupling of the string to the Dilaton Field is described by the following action integral:
The breakdown of conformal invariance would then be: \\\
With the beta functionals given by:
To impose conformal invariance, these beta functionals must vanish, as follows:
These are the field equations for the graviton, dilaton, and photon fields respectively. Notice that they have a rather fundamental basis, conformal invariance. We need to focus on this one:
I don;’t need to.
However, in the limit of little gravity, and no dilaton, this becomes the ordinary vacuum Einstein Field Equation.
String Theory is testable.
What does String Theory predict?
It predicts scattering amplitudes, caisimir energy, superpartners, gravitons, an infinitude of particles in a mass spectrum, gravitons, extra dimensions, AdS/CFT, and what not? Talking about AdS/CFT, see this recent paper by Raju and Papadogmias  (pdf here) and this one by Papawdogmias and Raju  (pdf here). This means the prediction of certain operators in the conformal boundary.
String Theory is testable at today’s energy scales.
Firstly, that isn’t a valid deleteion argument, as it is still testable.
Secondly, the Supersymmetry-related predictions of String Theory just depend on a certain number of parameters, called the Supersymmetry breaking parameters. For an supersymmetric string theory (like a manifold compactification of M-Theory), it is in fact possible to test the effects of supersymmetry, because the supersymmetry breaking energy parameter is low enough!.
String Theory has withstood experimental tests.
Huh, no. The only experimental result in contrary to the predictions of String Theory is probably  (PDF here). Other than this, String Theory has in fact been supported by experimental predictions. Also, the experiment does not rule out compactification lengths smallernthan half a milimetre.
String Theory has had experimental verification repeatedly.
See this article at the Mathematics and Physics Wikia (Introduction to String Theory) for the entire list.
Note that the 125 GeV Higgs actually serves as an experimental support for String Theory.
So basically, these criticisms of String Theory are just some ingeniously crafted Markov Chains, cooked up by a computer repairman at the Mathematics Department of the University of Columbia, aka the “Troll King“, and popularised by the popular media, such as “The Scientific American”, a magazine devoted to misleading laymen and making them even more unscientific.